*HEPAKATI0N OF INDELIBLE INK. - *>37 



IV. 



On the Preparation of Indelible Ink. In a Letter from 

 Mr. Thomas Sheldrake. 



To Mr. NICHOLSON. 



S IR, 



x\S your correspondent, Mr. Clofe, has alluded to my me- 

 moir on the nature and preparation of drying oils, it may not 

 be unpleafant to receive fuch information as I ara able to give 

 refpecling the object of his purfuit. 



By experiments repeated and varied every way that my iina- Amber is not 

 gination can fuggeit, I am convinced that amber is not fo- ^ 1 "^! e |" j ! 'jf 01 

 luble in alcohol or any eflential oil : it is foluble in exprefied 

 oils, by the procefs defcribed in Lewis's philosophical com- 

 merce of the arts, but that folution does not dry well, and The folution in 

 therefore will not anfwer Mr. Clofe's purpofe; but when dif- n*fg C 00 j f° r ink* 

 folvedby the * well-known procefs for making amber-varnifh, but the folution 



it is likely to anfwer extremely well. for varnifh is 



* J y good. 



There is another fubftance which feems likely to anfwer his Afphaltum pro- 



purpofe very well, f Afphaltum is a bituminous fubftance, mifes t0 be . a , 

 ,._,,,. . . , . r . . , r good material, 



perfectly black when viewed m a mals, but a dark transparent 



brown when diifolved : it is foluble in fpirit of turpentine at a 



* The following is the moft convenient method : Put fmall pieces Procefs for the 

 of amber into an iron ladle, fet it on a fire till they are melted, then 'ty foluton w 



timber 



add fo much of the beft drying oil as will make it liquid, ftir them 

 well together, and, when cold, add fo much fpirit of turpentine as 

 will make it thin enough to flow from the brufh. The object in 

 making varnifh is to difcolour the amber as little as poffiblej there- 

 fore it is but little roafted, and the lighteft coloured drying oil is 

 ufed } but if this folution of amber was ufed for making ink, the 

 darknefs of the colour would be an advantage, therefore the amber 

 fhould be thoroughly melted, and the darkeft drying oils ufed in 

 preference to the others. 



•f- Within thefe few years good afphaltum may be procured in pood afphaltum 

 many (hops in London : before that period it was unknown j the 1S now * a y 

 beft of what was fold, and is fill fold in fome places, was the caput 

 mortuum of amber j other compofitions of pitch and various refms 

 Were likewife fold for afphaltum. If it were ufed for Mr. Clofe's 



I ink, care mould be taken to feleft the beft. 

 low 



